1. Field of the Invention
The present invention relates to a vise which is mounted on the bed of a grinding machine thereby to fix a work in position or which is used to fix a work for a cutting operation.
2. Description of the Prior Art
A usual vise is made to have its one clamping jaw fixed to the base thereof and its other movable clamping jaw made movable toward and away from the stationary clamping jaw by means of a threaded rod. This threaded rod is made operative to move the movable clamping jaw over the movable range thereof, i.e., over the maximum stroke (within which the clamping operations can be effected by the stationary and movable clamping jaws).
In case the spacing between the stationary and movable clamping jaws is enlarged to clamp a larger work after a smaller work has once been clamped, or in case the opposite operations to the above are to be accomplished, it is desired that the movable jaw can be abruptly moved. For this purpose, it is also desired that the screw pitch of the threaded rod for effecting the clamping operation and the movement of the movable jaw be made to have a considerable value. With the pitch reduced, the movement of the movable jaw becomes reluctant. With the pitch excessively increased, the fastening force is weakened, while a high turning force being required, and the work once clamped is liable to become loose.
One of the vises for promptly changing the position of the movable clamping jaw while being free from the looseness after the clamping operation has been proposed and found in Japanese Utility Model Publication No. 50-45753 which was published for public inspection on Dec. 24, 1975.
In the vise disclosed in the above-specified publication, the leg is made to extend at an angle of 45 degrees from the bottom of the connecting member, which is held in the movable clamping jaw, through the through hole, which is formed in the bottom of the movable jaw, to a position below the base so that the pin carried on its leading end is brought into engagement with one of the transverse grooves which are formed in the bottom of the base. As a result, that portion of the movable jaw at the side of the stationary jaw, through which the through hole extends, has its thickness so reduced as to establish such a problem when used for clamping a heavy work that a crack is formed in the inner wall of the longitudinal wall which is formed to extend longitudinally along the center line of the base. This problem can be solved if the thickness of the movable jaw from the recess accommodating the connecting member to the portion facing the stationary jaw is increased. With this increase in thickness, however, since the portion of the movable jaw to be fixed to the base by the action of the connecting member, i.e., the intersection of the action lines in the so-called "composition of forces" goes farther from the work clamping sides, there arises another problem that the movable jaw becomes so instable that it is liable to float from the base.
It has therefore been found that the vise thus disclosed can be used to clamp a small work having a weight up to several ten kilograms but is not constructionally suitable for clamping a large clamp having a weight as heavy as several tons.